Method for making a side terminal weld

ABSTRACT

An integral and homogeneous connection between a terminal and a battery lug is accomplished without the requirement of specially shaped projections on either of the surfaces of the terminal or lug. Insulation is disposed between the lug and terminal and a portion of the overlapping area of the lug is pressed through an opening in the insulation means to make contact over a relatively small area with the terminal. Welding jaws are used to press the lug and terminal together and a current is provided by the welding jaws to heat up the area of contact so that the lead begins to melt in the opening. Since the lug and terminal are continuously squeezed together by the welding jaws, more cold lead is introduced into the opening until the entire opening is filled with molten lead from the lug and terminal.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention pertains to a method for making terminal welds in leadstorage batteries and to products produced by that method.

II. Description of the Prior Art

Lead storage batteries are often made with straps connecting theindividual plates in a stack together. The strap has a vertical portioncalled a lug. Terminals are provided in the battery for connection ofthe battery to external electrical cables, the terminals in somebatteries being positioned in the battery side walls. A portion of thesurface of the lug overlaps a portion of the inside surface of theterminal and the two must be connected together to form a goodelectrical connection. In one approach, the overlapping surfaces of thelug and terminal are pressed together by welding jaws andelectrically-welded connection is formed. One problem with this approachis that the overlapping area of contact creates a low electricalresistance resulting in insufficient heat at the interface causing acold weld.

Alternatively, it is known to provide the lug portion with a projectionwhich is inserted through a hole in a battery wall and into a hole orcavity on the terminal. A complete connection between the terminal andthe lug and a good seal between the terminal, battery wall and lug isobtained by exerting pressure on either side of the connection, that is,by applying pressure against the battery lug within the battery andagainst the terminal outside the battery so as to squeeze them togetherand seal the connection against the battery wall. If desired, the stepof fusing the connection together can be added by applying heat to thelug and to the terminal. See U.S. Pat. Nos. 3,457,118 and 3,303,056.

A similar approach to making electrical connections through storagebattery partitions or walls within the battery case is disclosed in U.S.Pat. Nos. 3,798,071; 3,723,699; 3,687,734; 3,589,948; 3,388,005; and3,313,658. In particular, the Allen U.S. Pat. No. 3,723,699 discloses amethod of making an intercell connection by providing a lug on one sideof a partition with a bar thereon which extends into a hole in thepartition wall. The lug on the other side of the partition does not havea bar but has a flat surface adjacent the partition. A specially shapedelectrode acts on the smooth lug, which has no bar, forcing the softlead of the lug to press into the hole in the partition wall against thebar on the opposite lug. Then, while under pressure, a current is passedfusing the two lugs together.

Problems can occur in obtaining precise alignment between the relativelylarge protrusion and openings on various parts to be connected togetheror between the protrusions and openings in a partition wall or a batterycase wall through which the protrusions must pass. In addition, the areaof contact between the protrusions on one part of the surface or openingon the other part is relatively large and requires a great deal of heatin order to melt the lead and fuse the parts together to form theterminal connection.

SUMMARY OF THE INVENTION

A lead terminal is positioned within an aperture in a battery wallforming a seal therewith. The cell in the battery which is adjacent theterminal contains a group of battery plates having a lug, a portion ofwhich is adjacent to and overlaps the inside surface of the terminal. Aninsulation means disposed between the lug surface and the insideterminal surface insulates at least a portion of the overlapping surfaceof the lug from a corresponding portion of the terminal.

Pressing the lug against the intermediate insulation means and theinside surface of the terminal creates a small area of contact betweenthe lug and terminal over a portion of the corresponding overlappingsurfaces which are not covered by the insulation means. Because the areaof contact is small, heat is generated in the region when current ispassed through the contact area, creating a fusion zone between the lugand terminal. Continual pressure is applied in pressing the lug andterminal surface together and additional cold lead is introduced intothe fusion zone causing more lead to melt creating an integral andhomogeneous connection between the lug and terminal and therebyeliminating cold welds.

Accordingly, it is an object of the invention to provide a method ofmaking a high quality side terminal weld and to provide a product madeby this weld.

This and other objects of my invention will become apparent from thefollowing description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a terminal sealed in a battery walladjacent to a battery lug;

FIG. 1a is a view of the lug, terminal and battery wall, taken asindicated along the lines and arrows 1a--1a in FIG. 1;

FIG. 2 is a cross-section of a lug, terminal and battery wall of FIG. 1with the preferred embodiment insulation in place;

FIG. 2a is a view of the lug, insulation, terminal and battery wall,taken as indicated along the lines and arrows 2a--2a in FIG. 2;

FIG. 3 is a cross-section of the lug, terminal, battery wall andpreferred embodiment insulation means of FIG. 2, showing the weldingjaws and an extruded portion of the lug in contact with the terminal;

FIG. 4 is a cross-section of the preferred embodiment of FIG. 3 with anelectrical potential shown schematically applied across the welding jawsand showing the integral and homogeneous connection between the lug andterminal being fused.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although specific forms of the invention have been selected forillustration in the drawings, and the following description is drawn inspecific terms for the purpose of describing this invention, thisdescription is not intended to limit the scope of the invention which isdefined in the appended claims.

Referring to FIG. 1, a portion of a battery wall 12 is shown having anaperture 16. The portion of the battery wall designated generally 13surrounding the aperture 16 comprises a ring 14 and an inwardlydepending flange 15. The ring 14 together with the inwardly dependingflange 15 create a partial chamber in the battery wall 12.

A terminal 10 is contained within the partial chamber engaging theinside surfaces of the inwardly depending flange 15 and the ring 14. Anextension 11 of the terminal engages the inside surface of the batterywall for a distance. In the embodiment shown here, the inside surface ofthe terminal 9 along its entire length is planar. The terminal is metaland may be lead alloy. Within the terminal a tapped hole 20 can beprovided.

The cell containing the terminal also contains a group of battery plateswith separators (not shown). A vertically extending lug 21, connected tothe strap of the group, has a portion adjacent and overlapping a portionof the inside surface 9 of the terminal 10. The adjacent and overlappingsurfaces of the lug and inside surfaces of the terminal are denoted 22and 23 respectively in FIG. 1.

FIG. 1a is a view along the lines and arrows 1a--1a of FIG. 1 showingthe inside surface of the battery wall 12, the inside surface 9 of theterminal 10 and a portion of the lug 21 overlapping a portion of theinside surface 9 of the terminal 10. The aperture 16 in the battery wall12 is shown as a circular dotted line 24 in FIG. 1a.

In FIG. 2, a preferred embodiment of the insulation means 100 is shownbetween the battery lug 21 and the terminal 10. The preferred embodimentinsulation means 100 has an aperture 102 and, except for this, theinsulation means covers the entire overlapping surfaces 22 and 23respectively of the battery lug 21 and the terminal connector 10. Thisis seen more clearly in FIG. 2a where the bottom edge of the insulationmeans is shown as the solid line 104 partially dotted where it isoverlapped by the lug 21. The aperture 102 in the insulation means 100is shown as a dotted circle in FIG. 2a.

In accordance with this invention, welding jaws are positioned on eitherside of the area to be welded. In FIG. 3, the external welding jaw 300contacts the outside surface 18 of the terminal at 301. The internalwelding jaw 302 has a protrusion 304 which is adjacent to the lug 21.The protrusion 304 engages the lug 21 on a surface 305 opposite theoverlapping surface 22.

A force is applied to the welding jaws moving the welding jaws towardone another. When this happens, the protrusion 304 contacts the lug 21along the surface 305, forcing the lug 21 to press against theinsulation means 100; the external welding jaw 300, pressed against theoutside surface 18 of the terminal 10 at the point 301, causes theinside surface 9 of the terminal to press against the insulation means100. The lug 21 is made of relatively soft metal such as lead alloy andwhen the lug 21 is pressed against the insulation means 100, the edge ofthe insulation means forming the aperture 102 acts as a die so that thesoft metal is extruded through the aperture 102 and contacts the insidesurface of the terminal along a small contact area 308. The shape of theextension 306 can be seen in FIG. 3 along with the area of contact 308.

The preferred embodiment insulation means is a flat, relatively thin,rectangularly shaped piece of material which is capable of electricallyinsulating the portion 22 of the lug surface which overlaps a portion 23of the terminal 10. At the same time, it acts to space apart theoverlapping surfaces of the lug and terminal and to thermally insulateone surface from the opposing surface. The insulation means must becapable of withstanding the compression-like force of the welding jawsand the extrusion of lead through the aperture 102.

When an electrical potential is applied across the welding jaws 302 and300 as signified by the plus and minus signs in FIG. 4, current beginsto flow between the metal lug and the metal terminal through therelatively small contact area 308 of FIG. 3 thereby generating a largeamount of heat in that region and causing the lead of the lug andterminal to melt, forming a fusion zone 400, shown cross-hatched in FIG.4. However, the welding jaws continue to apply a compressive-type forcesqueezing the lug and the terminal together and more cold metal or leadis introduced into the fusion zone in the aperature 102. As currentcontinues to flow and more lead continues to melt, the entire aperturewithin the insulation means is filled with molten lead to form ahomogeneous and integral connection in the fusion zone 400 between thelug 21 and the terminal 10. The current flow is stopped and the weldingjaws are retracted leaving the lug connected to the terminal.

It is important to note that no projections were present on either theterminal or the lug which might result in requirements for precisealignment and mating of the projection with either the lug or terminalnecessitating the implementation of elaborate alignment procedures eachtime a different size battery was introduced for terminal welding.Instead, in the preferred embodiment a projection 304 is provided on theinternal welding jaw 302 which presses against a substantially planarsurface of the lug. The other planar surface of the lug 21 pressesagainst a relatively flat insulation means 100 which can be positionedquite easily to have its aperature 102 align with the projection on thewelding jaw.

In an alternate embodiment of this invention, a battery case can beinjection molded to include plastic around the terminal connectorleaving an aperture 102 and thereby eliminate the separate insulationmeans from the battery. However, with the separate preferred embodimentinsulation means of this invention, there is no need to providedifferent terminal post sizes for different plate heights in differentsize batteries since the insulation means can be moved easily toaccommodate a common terminal post. For example, a series of batterieswith identical side wall terminal configurations, but with differentsize plate heights and lug lengths, might be presented for side terminalwelding. A smaller lug, in the area of the terminal overlap, will notextend as far toward the battery top as a longer lug. With the preferredembodiment insulation means of this invention, the insulation means canbe moved to insure that the aperture 102 will be positioned between thecommon terminal and either the longer lug or the shorter lug without theneed of varying the common terminal configuration.

In one embodiment of the electrical insulation means, a paper tape orpiece of cardboard with an aperture is provided with glue or adhesivealready applied to one side or surface. This is pasted to the terminalafter the terminal is assembled into the battery wall but before thegroups of plates and separators are added to the cells in the battery.

In lead storage batteries for automobiles, the groups of plates withineach cell are connected through partitions contained within each batteryby forming intercell connections, the cross-sectional area of which is atypical area of 0.4 to 0.5 square inches. In such a battery, theaperture within the insulation means, which ultimately becomes filledwith the homogeneous and integral connector formed between the lug andterminal, is of the same cross-sectional area of 0.4 to 0.5 squareinches. In applicant's preferred embodiment, the aperture in the papertape or card is circular and has a diameter of 0.375 inches. It will beseen that this aperture can easily be varied to provide a lug terminalconnection equal to the battery intercell connections for a variety oflead storage batteries.

In the preferred embodiment, a battery contains apertures 16 through thewall 12 of the battery case. Within the apertures formed in the wall 12of the battery case, terminals 10 are assembled which sealingly engagethe battery walls 12. A piece of paper tape or cardboard 100 having acircular aperture 102 therethrough adheres to the inside surface 9 ofthe terminal 10 in the battery aperture 16. A group of plates, insertedinto the cell containing the terminal, has a lug 21, which extendsupward from the plates adjacent to and overlapping the insulation card100 pasted on the inside surface 9 of the terminal 10. Welding jaws 300and 302 are then brought into contact with the terminal 10 and lug 21,the external welding jaw 300 pressing against the outer surface 18 ofthe terminal 10 and the internal welding jaw 302 having a projection 304thereon which presses against a surface of a lug. The lug 21 is sopositioned relative to the insulation 100 and terminal 10 that a portion22 of the lug surface overlaps a corresponding portion 23 of the insidesurface 9 of the terminal 10. The insulation means 100 covers an areawhich includes all of this overlapping surface 22 of the lug except forthe aperture 102. As the welding jaws squeeze, the lug contacts the edgeof the aperture 102 in the insulation material 100 and the soft metalbegins to extrude through the aperture 102 to contact the inside surface9 of the terminal 10. The area of contact 308 is quite small compared tothe area of the aperture 102 in the insulation 100. When electricalpotential is applied to the welding jaws, a current begins to flowthrough this small contact thereby creating a great amount of heat. Theinsulation surrounding the aperture not only provides an electricalinsulation so that only a small area of contact is provided between thelug and the terminal, but also provides a means of concentrating theheat at the point of contact by acting as both an electrical and heatinsulator. This concentration of the heat creates molten lead at thepoint of contact and with the jaws continually applying pressure to thelug and terminal, squeezing them together, more cold lead is extrudedinto the aperture 102 where it melts forming an integral and homogeneousconnection 400 between the lug and terminal.

It will be understood that various changes in the details, materials andarrangment of parts which have been herein described and illustrated inorder to explain the nature of this invention, may be made by thoseskilled in the art within the principal and scope of the invention asexpressed in the following claims.

I claim:
 1. A method for connecting battery terminals to battery lugs ina battery, said battery having a case having at least one terminalthrough a wall thereof, said battery case having at least one group ofbattery plates within a cell, said group having at least one straphaving a portion of a lug disposed adjacent and overlapping at least aportion of an interior surface of said terminal, said methodcomprising:(a) providing insulating material with an aperture definedtherein, between a portion of said overlapping lug surface and saidadjacent interior terminal surface; (b) pressing a portion of saidoverlapping portion of said lug to extrude said portion of said lugthrough said aperture to contact said terminal; and (c) resistancewelding at least that portion of said lug to said terminal whichcontacts said terminal to form an integral connector between saidterminal and said lug.
 2. The invention of claim 1 wherein said methodcomprises the step of positioning at least one internal welding jawinside said battery case and at least one outer welding jaw outside saidbattery case, said internal jaw having a projection thereon, saidprojection adjacent the opposite surface of said overlapping surface ofsaid lug and said projection aligned with said aperture.